very minor api tweak

lib/pry/code.rb

@@ -210,6 +210,7 @@ class Pry
     # @return [Code]
     def grep(pattern)
       return self unless pattern
+      pattern = Regexp.new(pattern)
 
       select do |l, ln|
         l =~ pattern

lib/pry/default_commands/input.rb

@@ -189,7 +189,7 @@ class Pry
           end
 
           if opts.present?(:grep)
-            @history = @history.grep(Regexp.new(opts[:grep]))
+            @history = @history.grep(opts[:grep])
           end
 
           unless opts.present?(:'no-numbers')